Bacteria in branches naturally fertilize trees

The bacteria in and on our bodies have been shown to be vital for human health, influencing nutrition, obesity and protection from diseases.

But science has only recently delved into the importance of the microbiome of plants. Since plants can’t move, they are especially reliant on partnerships with microbes to help them get nutrients.

Now, University of Washington plant microbiologist Sharon Doty, along with her team of undergraduate and graduate students and staff, has demonstrated that poplar trees growing in rocky, inhospitable terrain harbor bacteria within them that could provide valuable nutrients to help the plant grow. Their findings, which could have implications for agriculture crop and bioenergy crop productivity, were published May 19 in the journal PLOS ONE.

The researchers found that microbial communities are highly diverse, varying dramatically even in cuttings next to each other.

“This variability made it especially difficult to quantify the activity, but is the key to the biology since it is probably only specific groupings of microorganisms that are working together to provide this nutrient to the host,” said Doty, a professor in the UW School of Environmental and Forest Sciences.

Nitrogen fixation is a natural process that is essential to sustain all forms of life. In naturally occurring low-nutrient environments such as rocky, barren terrain, plants associate with nitrogen-fixing bacteria to acquire this essential nutrient.

It’s well documented that nitrogen fixation happens in bacteria-rich nodules on the roots of legumes such as soybeans, clovers, alfalfa and lupines. Bacteria help the roots fix atmospheric nitrogen gas into a form which can be used by the plant.